Radar systems using electromagnetic waves, in particular using microwaves having frequencies over 100 MHz, are widely known and are used for detecting objects and for determining velocities, distances, and directions of these objects.
The use of such radar systems in a motor vehicle for detecting the positions of preceding vehicles and possibly for lane assignment of these preceding vehicles is known.
A directional antenna provided in the particular radar system and having a radar sensor measures, in a manner essentially known, reflexes from waves incident on an object to be sensed (target object). The directional antenna may detect the object only if the direct path between the radar sensor and the target object is not concealed by another object or a plurality of other objects.
A target object may be concealed by another object in vehicle traffic, for example, in a sharp right curve of the highway, where the host vehicle moves in the left-hand lane behind a target vehicle at a relatively great time interval or approaches the latter, specifically in the case where another vehicle, for example, a truck, is moving in the right-hand lane and at least partially blocks the direct view between the radar sensor and the target vehicle, which therefore cannot be detected.
In the known radar systems, a radar sensor is now situated approximately in the vehicle center, preferably in the center of the vehicle's bumper, and the driver thus sits to the left of the sensor. This may cause the driver to be still able to see the target vehicle, although it is already concealed by the other vehicle for the radar sensor. In such a scenario, the target object is often lost, which is puzzling to the driver because of the target vehicle still being detected by the driver.
A concealment situation as just described occurs, for example, in traffic jams involving a plurality of vehicles and it often happens that potentially relevant target vehicles are briefly concealed by other vehicles even before they become relevant.
It is therefore desirable to improve the above-described radar system in such a way that measurement results that are puzzling or contradictory to the driver are avoided.